He was joined by a former Polish prisoner, 87-year-old Marian Turski, and the Chief Rabbi of Tel Aviv, Rabbi Israel Meir Lau, as he walked through the gate with the infamous "Arbeit macht frei" sign at the World War II camp in southern Poland.

"I pay my deepest tribute to the victims and survivors of the Holocaust, a most terrible horror in human history," Ban wrote in the memorial book at the site's museum.

"The United Nations is strongly committed to the vital work of Holocaust remembrance and education, and to building a world of equality and dignity for all," he added, according to AFP.

Ban laid a wreath at the foot of the wall where the Nazis shot prisoners, before pausing in thought before a barbed wire fence.

Six million European Jews died during Nazi Germany's campaign of genocide in World War II. In addition to Jews, more than 100,000 others including non-Jewish Poles, Roma, Soviet prisoners of war and anti-Nazi partisans, were killed in Auschwitz-Birkenau.

With Monday’s visit, Ban became the first UN leader in history to visit Auschwitz. He flew in to Poland from neighboring Lithuania, current holder of the rotating half-year EU presidency, for the three-day visit.